The proposed investigation is focused on improving understanding of the molecular dynamics of the lipid components of human plasma lipoproteins and related structures. The primary experimental probe employed is natural abundance carbon-13 NMR spectroscopy. Particular attention will be directed toward the following systems: 1. normal high- and low-density lipoproteins; 2. lipoproteins derived from patients with familial hyperlipoproteinemias or diseases leading to the production of LP-X; 3. phospholipid liposomes containing both cholesterol and lipoprotein apoproteins; and 4. arterial tissue containing advanced plaques. In addition, we will examine several of these systems following enzymatic modification by those enzymes, particularly LCAT and lipoprotein lipase, that normally metabolize lipoproteins.